Nature's Gentleman was a play on "Nature's Nobleman."
Could not find author's name but herewith the poem as recollected :

Nature's Nobleman.

Away with false fashion, so calm and so chill,
Where pleasure itself cannot please,
Away with cold breeding, that faithlessly still,
Affects to be quite at its ease;
For the deepest in feeling is highest in rank,
The freest is first in the band,
And nature's own nobleman, friendly and frank,
Is a man with his heart in his hand.

Fearless in honesty, gentle yet just,
He warmly can love and can hate,
Nor will he bow down with his face in the dust
To Fashion's intolerant state;
For best in good breeding, and highest in rank,
Though lowly or poor in the land,
Is nature's own nobleman, friendly and frank,
The man with his heart in his hand.

His fashion is passion, sincere and intense,
His impulse simple and true,
Yet tempered by judgment, and taught by good sense;
And cordial with me, and with you:
For the finest in manners, as highest in rank,
It is you! man! or you, man! who stand
Nature's own nobleman, friendly and frank,
A man with his heart in his hand!